JPS634072A - Catalytic solution for electroless plating and its production - Google Patents

Abstract

PURPOSE:To obtain a catalytic soln. enabling satisfactory electroless plating on an electrically insulating substance by aging an aqueous soln. contg. palladium chloride, hydrochloric acid, sodium chloride, stannous chloride and alpha,alpha'- dipyridyl each at a specified concn. at a specified temp. CONSTITUTION:An aqueous soln. prepd. by dissolving 0.1-1g/l palladium chloride (PdCl2), 3-30g/l stannous chloride (SnCl2.2H2O) and 1-100mg/l alpha,alpha'- dipyridyl in an aqueous soln. contg. 10-50ml/l hydrochloric acid (37%) and 5-150g/l sodium chloride is aged at >=80 deg.C to produce a catalytic soln. When an electrically insulating substance such as plastics is activated by treatment with the catalytic soln., perfect electroless plating can be carried out.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a catalyst solution for electroless plating and a method for producing the same, specifically for activating an electrically insulating material, especially plastic, to prepare it for a metal coating process by electroless plating. This invention relates to a palladium catalyst liquid and a method for producing the same. (Prior Art) In general, in the electronics industry, it is widely practiced to coat plastics with metals by electroless plating to make them conductive. After forming a through hole at a location, a catalyst for electroless plating is adsorbed on the wall of the through hole, and then a metal coating is applied to the wall surface of the through hole by electroless plating such as electroless copper plating to make the wall surface of the through hole conductive. Palladium metal is widely used as a catalyst for electroless plating, and palladium metal is formed on the walls of the through-holes by bringing the walls of the through-holes into contact with a mixed colloidal aqueous solution of stannous chloride and palladium chloride. After washing with water, the tin compound adsorbed at the same time as the palladium metal must be removed by immersion in a hydrochloric acid solution or a fluoroboric acid solution to expose the palladium metal. 56-10377, palladium chloride Ig/Q, stannous chloride 10-60 g IQ, hydrochloric acid (37
% solution) 8 mQ/Q, the composition of sodium chloride 58 mQ/Q is disclosed. [Problems to be Solved by the Invention] However, these mixed colloidal aqueous solutions of stannous chloride and palladium chloride do not have sufficient adsorption properties on plastics and glass, and this often causes the through-hole walls of copper-clad revoxy resin laminates to become sticky. This caused deposition defects (pinholes, voids, etc.) in electroless copper plating. [Differences between the invention and the prior art] The purpose of the present invention is to provide a catalyst solution for electroless plating that eliminates the drawbacks of the prior art and a method for producing the same, and in particular, to provide a catalyst solution for electroless plating that eliminates the drawbacks of the prior art.
α, which has the effect of promoting the reduction reaction of
The invention is original in that α'-dipyridyl is contained in the catalyst liquid. [Means for solving the problems] The present invention provides palladium chloride (PdC et al.) per aqueous solution IQ.
0.1 to Ig, 10 to 50 ml of hydrochloric acid (37% solution),
50-150 g of sodium chloride, stannous hydrochloride (SnCQ)
2.2H20) A catalyst solution for electroless plating characterized by containing 3 to 30 g and 1 to 100 g of α, α'-dipyridyl, and an aqueous solution containing hydrochloric acid and sodium chloride containing palladium chloride, stannous chloride and α , α'-dipyridyl is added and dissolved, and then the aqueous solution is aged at a temperature of 80° C. or higher. [Principle/Action] α,α′-pyridyl in the catalyst liquid for electroless plating (hereinafter abbreviated as catalyst liquid) of the present invention promotes the reduction reaction of palladium chloride with stannous chloride, and forms a stable palladium metal colloid. Facilitates the formation and adsorption of palladium metal onto plastics and glass. The concentration of α,α′-dipyridyl in the catalyst solution is 11g/Q
When it is lowered further, the effect of promoting adsorption of palladium metal is significantly reduced. Also, the concentration of α, α′-dipyridyl is 100 m
When g#I is exceeded, the copper foil tends to discolor when a copper-clad epoxy resin laminate is treated with a catalyst solution. α, α′−
In addition to the above effects, dipyridyl also has the effect of masking iron ions contained as impurities in the catalyst liquid and stabilizing the catalyst liquid. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples. (Example 1) 40 mA of 37% hydrochloric acid was added to 700 ml of pure water, and 100 g of sodium chloride was then dissolved. Next, 1 g of palladium chloride was dissolved, and then stannous chloride (Sn
CR, -28,0) 20 g and α,α'-dipyridyl 2
After dissolving 0 mg, the liquid temperature was raised to 85°C and aged for 30 minutes. The color of the liquid changed from black edge color to blackish brown, indicating that a mixed colloid of palladium chloride and stannous chloride was produced. As a comparative example, when an aqueous solution containing no α,α'-dipyridyl was aged at the same liquid temperature, the color of the liquid changed from black edge color to blackish brown, and it took about 1 hour to show the same absorbance as the above liquid. . This proved that the reduction reaction was promoted by the stannous ion (S n + + ) of the palladium ion in α,α'-dipyridyl. After cooling to room temperature, pure water was added to the whole to make it IQ, and the catalyst A liquid was prepared. A copper-clad epoxy resin laminate with through-holes formed in this catalyst solution was immersed for about 5 minutes, then rinsed with water, and further immersed in a 5% aqueous fluoroboric acid solution for 5 minutes to form a copper-clad epoxy resin laminate together with metallic palladium. Chloride adsorbed on the wall of the through hole of the plate
Tin compounds such as tin are removed and the metal palladium in the through-hole wall soil is activated. Next, it was immersed in an electroless copper plating solution having a water washer temperature of 25° C. and a pH of 13 for about 15 minutes to deposit an electroless copper plating film on the wall of the through hole. The wall of the through hole was completely covered with an electroless copper plating film. − α as a comparative example. A copper-clad epoxy resin laminate was treated in the same manner as above using a catalyst solution to which α'-dipyridyl was not added, and electroless copper plating was performed. Pinholes were observed. (Example 2) A copper-clad epoxy resin laminate was prepared in the same manner as in Example 1 using a catalyst solution prepared by diluting the a,α'-dipyridyl-containing catalyst solution in Example 1 twice with pure water. When the plate was subjected to electroless copper plating, the walls of the through holes were completely covered with an electroless copper plating film. [Effects of the Invention] As explained above, by treating with the catalyst liquid of the present invention, the walls of the through holes in the printed wiring board can be completely covered with an electroless plating film, improving the reliability of the electrical connection of the through holes. It has the effect that it can.

Claims (2)

[Claims] (1) Palladium chloride (PdCl_2
) 0.1-1 g, hydrochloric acid (37% solution) 10-50 ml,
50-150 g of sodium chloride, stannous hydrochloride (SnCl
_2.2H_2O) 3 to 30 g and α,α'-dipyridyl 1 to 100 mg. (2) Palladium chloride, stannous chloride and α,α'-dipyridyl are added and dissolved in an aqueous solution containing hydrochloric acid and sodium chloride, and then the aqueous solution is aged at a liquid temperature of 80°C or higher. A method for producing a catalyst solution for electrolytic plating.